During EHV transmission system towels and lines design

the structure of conductors and towers was designed independently.Because of the difficulty to calculate the longitudinal unbalanced tension of towers

it is generally verified by taking the percentage of the conductor maximum design tension according to regulations.However

the unbalanced tension is one of the important factors impacting the safety of transmission lines

so accurate calculating the longitudinal unbalanced tension caused by span

height difference

and uneven load is meaningful.In this paper

the beam element and the cable element were used to establish integral unit model

spatial finite element calculation of icing load for transmission system was conducted

and the ultimate load-carrying capacity was calculated under the even ice load circumstance

and the causes for collapsed towers were analyzed under the condition of real uneven icing load.The weakness of the transmission line was pointed out and modification proposals were presented.